refactor(chatgpt): bind the coerced input instead of rebinding the parameter

Greptile flagged the parameter rebinding and the explanatory comments against
the repo conventions in CLAUDE.md, which bans rebinding a function parameter
(LIT011) and keeps comments to suppressions, TODOs and genuinely complex logic

Bind a Final local for the coerced input rather than reassigning `input`, and
drop both prose comments; the rationale lives in the commit and the PR body
rather than duplicated at the call site. The mutable-ok suppression stays,
since it is the allowed kind and the list is still constructed

Behaviour is unchanged: 24 tests pass, and the same 4 fail with only the
provider file reverted to base

Signed-off-by: Alexander Chernov <alexander@chernov.it>

litellm/llms/chatgpt/responses/transformation.py

@@ -66,13 +66,14 @@ class ChatGPTResponsesAPIConfig(OpenAIResponsesAPIConfig):
         litellm_params: GenericLiteLLMParams,
         headers: dict,
     ) -> dict:
-        # The Responses API accepts a string or a list, but this backend
-        # rejects a string with {"detail": "Input must be a list"}.
-        if isinstance(input, str):
-            input = [{"role": "user", "content": input}]  # mutable-ok: the wire payload this backend requires
+        coerced_input: Final = (
+            [{"role": "user", "content": input}]  # mutable-ok: the wire shape this backend accepts
+            if isinstance(input, str)
+            else input
+        )
         request: Final = super().transform_responses_api_request(
             model,
-            input,
+            coerced_input,
             response_api_optional_request_params,
             litellm_params,
             headers,
@@ -103,8 +104,6 @@ class ChatGPTResponsesAPIConfig(OpenAIResponsesAPIConfig):
             "reasoning",
             "previous_response_id",
             "truncation",
-            # The chat-to-responses bridge translates response_format into
-            # "text"; dropping it here discards strict schemas silently.
             "text",
         }